Radiation Bioeffects , Risks , and Radiation Protection in Medical Imaging in Children

Diagnostic imaging has evolved from the single technique of radiography discussed in the first edition of Caffey’s Pediatric X-Ray Diagnosis in 1945 to a specialty with many modalities and techniques. Many of these modalities use ionizing radiation, and some, such as computed tomography (CT) and nuclear imaging, entail relatively high doses of radiation. Therefore the imaging community (and our medical colleagues) must jointly adhere to two of the principles of radiation protection for our patients: justification (i.e., the examination is warranted) and optimization (i.e., the appropriate technique is used). For example, in computed or direct digital radiographic examinations, image processing can accommodate overexposures. The image can be adjusted to appear as if it were obtained using standard techniques, whereas with screen film technology, the film image would be recognized as overexposed (dark) (Fig. 1.1). Without accountability for displaying dose metrics (such as the exposure index available with digital radiography), it is difficult or impossible to account for patient exposures in clinical practice. Additionally, uninformed and potentially irresponsible justification of medical imaging occurs when persons are unfamiliar with the methods of estimating an effective radiation dose during CT examinations in children. Increasing accountability is expected from the medical community with regard to the use of imaging modalities that expose children (as well as adults) to ionizing radiation. As such, a basic understanding of radiation biology, including bioeffects, radiation doses of various types of imaging examinations, and risks of radiation, is essential for the pediatric imager. A glossary of terms and dose descriptors is found in the addendum at the end of this chapter.